The invention relates to a threshold circuit for radar video signals where the radar coverage is divided into zones constituted by azimuth sectors and range rings, the zones being subdivided into cells formed by radar scans and range quants, which threshold circuit comprises a first cell-averaging circuit for determining, from the video signals received in the individual cells, the average echo strength in each zone pertaining to the azimuth sector that has been scanned by the radar beam.
The German Auslegeschrift No. 24 40 742 and the German Offenlegungsschrift No. 28 50 508 describe circuits for the suppression of clutter areas and stationary targets, where the radar coverage is divided as stated above and where the average echo strength is determined in each zone. In the circuit described in the Auslegeschrift this average echo strength is compared with that of zones adjoining in azimuth and range to establish the presence of clutter areas. In the circuit described in the Offenlegungsschrift the average echo strength obtained for each zone is integrated over several antenna revolutions to indicate the presence of stationary targets.